Molds for electroslag refining



1 June 10, 1969 IP.T.R.MASKALL 3, ,7

MOLDS FOR ELECTROSLAG REFINING Filed April 10, 1967 United States Patent3,448,790 MOLDS FOR ELECTROSLAG REFINING Peter Thomas Reginald Maskall,Birmingham, Warwickshire, England, assignor to Associated ElectricalIndustries Limited, London, England, a British company Filed Apr. 10,1967, Ser. No. 629,746 Claims priority, application Great Britain, Apr.12, 1966, 15 999/66 Int. Cl. mid 27/04, 11/12 U.S. 164-348 4 ClaimsABSTRACT OF THE DISCLOSURE Within the drainage trough of an open-curtainwatercooled mold for electroslag refining there is set up, at a smalldistance from the mold wall, a barrier defining an Background of theinvention This invention relates to the so-called electroslag process ofproducing ingots of refined metal, which word is used herein asconnoting not only elemental metals but also, in accordance with animportant present day use of this process, metal alloys such forinstance as various types of steel.

In the electroslag process, a consumable electrode of the metal to berefined, or possibly of the unalloyed constituents of an alloy to beproduced in refined form, is melted into a pool of molten slag, in awater-cooled mold, the metal re'solidifying to form an ingot. Theprocess was previously carried out in a water jacketed copper mold, buta recent improvement has been the use of a thin wall steel mold cooledby an open. curtain of water flowing freely down its outside. Such amold is not only less expensive but is also safer in operation, sincethe effectivene'ss of the cooling can be observed and steps taken tocorrect any local overheating. If breakout does occur, the water is atatmospheric pressure and there is no confined jacket or chamber in whichdangerous vapour or gas pressures can be generated. Repair is simple andcheap.

The water is collected in a drainage trough round the base of the mold,after it has run down the side of the mold, and it is found that theretends to be a pocket of relatively stagnant water at the corner formedby the mold wall and the base of the trough. With a drainage system inwhich water collects to a depth of l"-2" in the trough, the curtain ofwater, freely falling under gravity and restrained by the drag of themold side, does not strike the surface of the accumulated water withsuflicient velocity to disturb it effectively. Even with a veryeffective drainage system which may have a drain hole in the base of thetrough and in which the water may possibly be only a fraction of an inchdeep at the base of the mold, the water flowing down the mold wall isunlikely to cool sufficiently effectively the necessarily sharp cornerbetween the wall and the base: the Water may rebound from the base ofthe trough, forming air pockets and voids.

'Ihe mold is in itself open-bottomed but is seated on a water-cooledclosure base from which it can be separated to give access to the ingotat the end of the process. During the start of the process, very intenseheat is liberated in the mold base and breakouts of slags and metal andwelding of the newly formed ingot to the mold are likely to occur ifsteam pockets are allowed to form at this critical bottomoorner. Thepresent invention seeks to eliminate or reduce the formation of suchpockets.

Summary of the invention According to the invention, a mold forelectroslag relining is provided with an open-curtain water-coolingsystem and also has a drainage trough which surrounds a portion of theheight of the mold adjacent to its lower end and within which at a smalldistance from the mold wall there is a barrier defining between itselfand the mold wall an open-topped peripheral space, together with meansfor so introducing cooling water into the space as to create a flow ofwater which is closely confined against the mold wall by the barrier andmilitate's against the formation of a stagnant water pocket at a cornerformed by the mold wall and the drainage trough. Said means may bearranged to direct the cooling water into the space peripherally thereofand preferably, if (as would usually be the case) the space is annular,tangentially thereof so as to establish a circulatory flow.

Brief description of the drawings In order that the invention may bemore clearly understood, an embodiment thereof will now be described byway of example with reference to the accompanying drawing in which:

FIG. 1 is a somewhat schematic cross-sectional elevation of a mold andcooling system therefore in ac cordance with the invention; and

FIG. 2 is a plan View cross-sectioned on the line A-A in FIG. 1.

Description of the preferred embodiment Referring to the drawings, themold is shown at 1, seated on a water cooled closure base 2 with acircular drainage trough 3 surrounding and welded to its lower end.Between the base .2 and the trough 3 there is a sealing gasket 3A:towards its inner diameter, the gasket is composed of some heatresisting material such as asbestos; towards the outer diameter, a moreeffective sealing material, such as rubber, is employed. A water curtainflowing down the outside of the mold .1 is provided by jets of waterspraying on to the outside of the mold from an annular header 4. Inaccordance with the invention, within the trough 3 an inner circularbarrier or wall 5 is set up about 1" away from the mold wall itself.This barrier makes a substantially water-tight joint with the base ofthe drainage trough and extends upwards for 2"3" so that its upper edgeis above the normal water level in the trough but below the outerboundary wall of the trough. An open-topped annular space 6 is thusformed round the .bottom of the mold, and into this space an auxiliarycooling water supply is introduced by means of one or more tangentiallyapproaching pipes 7. This auxiliary supply can conveniently (but notnecessarily) be the water discharged from the water cooled base on whichthe mold rests, as indicated in the drawing by the provision of thelinking pipe 8: sometimes this supply may, with advantage, beindependent of the supply to the base.

The restricted cross-section of the annular space causes the auxiliary'water supply to spiral vigorously upwardly round the mold base, tooverflow the barrier 5 into the main drainage trough 3. The rw ater isin vigorous movement against the mold wall until it overflows thebarrier, at which point it is joined by the water flowing down the wall.There is thus no point at which water is stagnant and little possibilityof the formation of steam pockets: indeed, the water should be suppliedsufficiently forcefully to cause violent agitation thereof against thebottom corner between the mold wall and the trough.

I claim:

1. A mold for electroslag refining provided with an open-curtainwater-cooling system and also having a drainage trough which surrounds aportion of the height of the mold adjacent to its lower end and within(which at a small distance from the mold wall there is a barrierdefining between itself and the mold wall an open-topped peripheralspace, together with means for so introducing cooling water into thespace as to create a flow of water which is closely confined against themold wall by the barrier and militates against the formation of astagnant Water pocket at a corner formed by the mold wall and thedrainage trough.

2. A mold as claimed in claim 1, with said means arranged to direct thecooling water into the space peripherally thereof so as to establish acirculatory flow.

References Cited UNITED STATES PATENTS 8/1961 Armand et al. 1642832/1963 Cooper et al. 164348 J. SPENCER OVERHOLSER, Primary Examiner.

JOHN S. BROWN, Assistant Examiner.

US. Cl. X.R. 164-283; 249-79

